What is "Headspace"?

[Old Fud]

I keep hearing the term.

When it's used, it seems to be important.
What is it?
When does it matter and why does it matter when it does?

How do you know what it is supposed to be?
How do you know what it is?

dumb fud

 

[Infidel]

In a firearm, headspace is the distance between the bolt face and some datum in the chamber. If it is chambered for a rimmed cartridge, then it is the distance to the face of the breech where the forward side of the rim will contact. For bottle-neck cartridges, it is the distance to a "datum ring", more or less the center of the shoulder. For belted magnums, it was originally to the face where the forward side of the belt would contact, but manufacturers got sloppy enough that they just headspace on the shoulder nowdays. Rimless straight cartridges, like .45 ACP, headspace on the mouth of the case.

Another way of saying it is that headspace is the distance from the bolt face to whatever stops the cartridge from going further forward into the breech.

If headspace is too tight, then the cartridge won't go into the chamber.

If the headspace is too loose, which is the condition that we most often worry about, then when the cartridge is fired, the case head has room to stretch and can fail.

To check the headspace, use a set of GO/NOGO gauges from Brownell's or Midway or wherever. If the GO gauge doesn't go, then the headspace is below minimum and cartridges made to SAAMI dimensions will not chamber. If the NOGO gauge goes, then the headspace is over maximum and the gun is dangerous. You can also get a FIELD gauge, which is similar to NOGO, but if it goes, then the headspace is at or near maximum and the firearm should visit a gunsmith.

 

[1911Tuner]

Headspace

Infidel...Gawd...that was beautiful, man! Ya took the words right outta my mouth. Welcome aboard, sir. Welcome aboard!

 

[P95Carry]

Infidel - welcome. Tuner knows way more than me but I too will endorse your very nice and succint definition. Nice job.

 

[Jammer Six]

Speaking of headspace, and in light of the discussion we had here last month about it, I was watching the AGI video last night, and darned if he (Glen Shuey) didn't demonstrate checking headspace with a live round, and with a Go/No-Go gauge in a barrel without installing it in a slide.

Now, how is that possible?

 

[1911Tuner]

Shuey's Headspace

Ohgod! Here we go again...

Howdy Jammer,

That's known as a "Barrel only headspace check" done to determine chamber depth relative to chamber hood, but it's NOT a reliable indicator of safe or correct headspace. See Kuhnhausen, Voume 2, Page 106: Figures 91 and 92.
pay particular attention to Figure 92.

Cheers!

 

[Jammer Six]

Thanks, 'Tuner!

 

[Infidel]

Thank you, 1911Tuner and P95Carry, for your kind words. I didn't mean to jump into someone else's domain, and I must have cruised by the question, originally posted in the "General" forum, right after it was posted, before it was moved.

 

[1911Tuner]

Domain

Howdy Infidel,

This headspace thing was a hot-button topic for a while, and we had several
posts indicating that it wasn't fully understood by all. No sin there. Not everybody understands all facets of several issues...but the matter could have been settled by simply opening any one of several reloading manuals
available and looked at the definition in the glossary...which pretty much states what you posted here, albeit not in as much good detail as yours.

As far as the gunsmithing video that Jammer mentioned...I've never seen it,
and can't comment. Like Kuhnhausen's manuals, I had to wait until I actually read'em. Now that I have, I recommend them highly...not only for the 1911
Colt-Browning pattern pistols...but for all the other designs that they cover.
One day, I'll have a peek at the video and see for myself.

If anyone is willing to loan me a copy, I'll pay shipping and insurance both ways.

Standin' by...JAMMER <-----*hint hint*

 

[Jammer Six]

Standin' by...JAMMER <-----*hint hint*

Lemme see what I can do, old man.

I'd be interested in hearing what you think of it.

 

[1911Tuner]

Old

Old man? OLD MAN???

Why you young If'n I was 15 years younger I'd...I'd...uh......... Awhell, nevermind...I forget.

 

[Old Fuff]

HOW DARE HE CALL YOU "OLD MAN ....??"

I CLAIM THAT TITLE ...

 

[P95Carry]

''OLD MAN''?? ... hey Fuff, you can't claim any exclusivity rights ya know!!

 

[Jammer Six]

Speaking of which, that thumb safety you sent me is now in service, after the thumb safety on my SA milspec BROKE...

So, thanks, old man.

A lot.

 

[Old Fuff]

You put that gen-u-ine United States Government real-steel part into an in-free-yor Springer pistol ..... ??

THAT DOES IT!! I'M GOING TO TAKE MY JERRY-TOL AND GO TO BED (WIMPER) DON'T KNOW WHAT THE WORLD IS COM'MON TOO ... NEXT THING YOU KNOW YOU'LL BE GETTING A TRIGGER WITH HOLES IN IT.

DARN!! WHERE DID I PUT THE HOT WATTER BOTTLE ...?? :banghead:

 

[P95Carry]

Fuff ... I am gettin' worried about ya ... ages since I have seen you shouting like this!!

 

[Old Fuff]

BUT (BLUBBER) HE PUT MY GUN-U-INE, UNITED STATES GOVERNMENT/WW II SAFETY LOCK (SOB!) INTO ONE OF THOSE MIM CON-TAM-I-NATED SPRINGER CLONES. (GASP ... SOB ... BLUBBER).

IF ONLY I HAD KNOWN IT WOULD COME TO THIS ....

 

[P95Carry]

Sleep on it dude - all will seem less bad in the morning ... until the next time

 

[Old Fuff]

Oh thank you ...

Should I take two aspirins first ...??

 

[sm]

Skip the Asprins - eat a Fried Apple Pie.

If folks would buy them polymer guns and such - then there would be no need to ship old steel parts to fit newer similar designs.

Old Fuff would not get upset , would not have yell, sob, whimper, or eat a Fried Pie before bed. He could hold onto his parts and use them on old guns that are traded for new polymer ones.

It's for the Respect of our Elders

I don't recall , and don't have my copy of Hallock's Book. Did Hallock discuss headspace?

I don't have the 1911 book by Kuhnhausen. Got his on S&W Revos tho'

Sheesh - my want list for books is growing such...

 

[1911Tuner]

Thumb Safety

Thumb safety broke...That would NOTTA been a good thing if you hadda been
UTYAIA.

Anybody know what the headspace specs is on a fried pie?

 

[Bill Z]

Out of curiosity, who else, besides Kuhnhausen, who was a general smith, would you trust with barrel issues? Is there any authority on the matter who's body of work you would go by? We have several manufacturers of barrels, Fred kart, Wil Schuemann, the folks at Briley and Barsto also. Let's limit it to the 1911 since this has been the topic of discussion. You know, this might even make a good poll, just don't know how to post it or word it. It seems we trust their barrels, what about their advice?

 

[1911Tuner]

Trust

I trust the original designers and engineers who first established those headspace dimensions and the methods for verifying them. While I'm sure that many barrel manufacturers do hold their chambers to exacting dimensions
and don't feel that gauging headspace is an necessity...I also learned long ago that there is no such thing as a perfect dimension...and that
sometimes allowable tolerances are exceeded by various manufacturers and
that anything can happen to a machining jig or fixture. It takes very little time to verify correct, safe headspace...and when it's my hands and eyes on the table, I'll do the check...I don't care who built the gun. I've seen too many pistols...ranging from the very expensive to the bottom feeders...that
barely made it...and a good many that didn't. Thompson Auto Ordnance pistols that wouldn't readily close on a minimum GO gauge...and Les Baers that would close on a NO GO.

Consider it rather like taking another man's word for it that the gun ain't loaded. You'll excuse me if I verify that for myself, thank you. I won't take your word for it, and I don't expect you to take mine. The same goes for headspace. It's one of the first things that I do, even on new guns...even on new, expensive guns. You'd be surprised what a set of headspace gauges can reveal. How about a new M-70 in .300 Win Mag that bolted on a SAAMI standard NO GO gauge?

Whom do I trust? Me and my little old gauges.

 

[Bill Z]

Does this mean we need to guage every cartridge with a case guage before we shoot it? Couldn't those same tolerances be off on a cartridge? Couldn't they/wouldn't they have a similar/same cause and effect? If so, how can we trust anything we just pull out of a box and stuff in a chamber? Geeze, you guys have got me terrified to shoot now.......................NOT.

 

[Bill Z]

Let me add this to the equasion. What is the tolerance of the guages. Don't they produce roughly .010 headspace? Couldn't this present a problem on high pressure rounds like the 38 Super. On those rounds would final reaming be better determined on the actual case size, assuming we have checked for proper case legnth. I know on a .45ACP .010 is no biggie, but what could that amount of headspace lead to in a hot 38 Super?